Low-pressure Catalytic Oxidation Process Lead Anode Mud Process

A new process of lead anode slime treated by catalytic oxidation system under low oxygen pressure is developed in this paper, the theory of which is analyzed, and small scale researches in the lab and semi-industrial experiments are also carried out. The main contents and conclusions are as follows:1. The paper concludes the domestic and overseas situations on the lead anode slime treatment and pressure leaching firstly, analyzes their pros and cons, and provides the process of catalytic oxidation treatment under low oxygen pressure against the disadvantages.2. The E-pH diagrams of Pb-S-H2O and AgaSb-HiO are calculated and drawn, and the thermodynamics of oxidation leaching of the lead anode slime is systematically analyzed with reference to a series of E-pH diagrams of Cu-H2O, Ag-H2O, Pb-H2O, Sb-H2O, Bi-H2O, etc.3. The mechanism of nitric acid catalysis is systematically analyzed, and the reaction equilibrium and velocity of oxidation and absorption of the nitrogen oxide are also discussed in detail.4. The small scale experiments on the application of the process are carried out and the optimum conditions on the lead anode slime treatment are given as follows: 350g/L sulfate acid,95g/L nitric acid, 5:1 liquid-solid ration, 48 initial temperature, 2.5 hours' oxidation leaching time, and successive supplying oxygen to ensure that the NO can be completely changed to NO2. With the conditions above, the oxidation leaching ratio of Cu, Bi and As are all more than 99.8%.5. In order to verify the feasibility of the process, much better reaction conditions are given by semi-industrial experiments: 400g/L initial sulfate acid in the leaching solution; 0.45g nitric acid per gram of sponge copper; about 8:1 liquid-solid ratio; 1.5m3 leaching solution; 40 initial temperature; 2 hours' oxidation time. With the conditions above, leaching rate of Cu and Ni are more than 99%.6. The result of experiments demonstrates that with the characteristic that nitricoxides produced by the oxidation reduction reaction the nitric acid participated in can be absorbed in water and nitric acid is reproduced, the consumption of nitric acid can be reduced and the recovery rate of which in semi-industrial experiments are up to 70%, and higher ratio can be reached by further developments, which makes it possible for nitric acid as a oxidant in material treatment.7. It is demonstrated in lab and semi-industrial experiments that by controlling the operation procedure, catalytic oxidation leaching reaction can be carried out under much lower pressure (60mmHg relative pressure in lab experiments, 300mmHg lower in industrial experiments). As a result, the low demand for the equipments, low cost or reequipment of present equipments without other special matching equipments, simplified operation and low consumption are the characteristics of the process.8. The oxidation ratio in catalytic oxidation system under low pressure is very high, besides, the process can treat not only metallic material but some kinds of metal sulfide, in which low valence sulphur is oxidized to free sulphur left in the residue.